In recent years, users who send content stored in a stationary recording device to a portable terminal and enjoy the content outside, or users who exchange content with friends' portable terminals or send their own content to friends' portable terminals are increasing in number. In addition, the stationary recording device includes a PC and a recorder in households, and the content includes an image and a moving image, and the portable terminal includes a mobile phone.
A communication direction and a communication range of a portable terminal are different between a case in which a user puts own portable terminal and a friend's portable terminal closer to each other to communicate to exchange content, and a case in which a user communicates to send content to a distant television in a house using own portable terminal.
For example, for communicating with a nearby device, communication is made using radio waves for a short distance from a rear surface of a portable terminal. Meanwhile, for communicating with a distant device, communication is made using radio waves for long distances from a side surface of a portable terminal. As described above, the communication direction and the communication range are different depending on the usage purpose. The communication direction indicates a place of a communication terminal to which radio waves are transmitted.
A radiation pattern variable antenna or a sector antenna is used for switching the communication direction and the communication range. The sector antenna is an antenna in which a plurality of antennas having directivity are arranged so as to obtain directivity in every direction and one of antennas is selected and used to obtain a desired directivity. The radiation pattern variable antenna is an antenna in which directivity arbitrarily varies by controlling a phase of electric current fed to a plurality of antennas.
A technique disclosed in Patent Literature 1 has been known as a related art relating to such a radiation pattern variable antenna or a sector antenna. The sector antenna covers a broad communication range by switching a plurality of antennas having directivity in different directions, for example, four directions. In addition, the radiation pattern variable antenna freely changes overall antenna directivity by controlling a phase of electric current fed to a plurality of antennas and changing a direction in which radio waves emitted from a plurality of antenna elements are combined and offset each other.